Solid zeolites

Hydroxylation of benzene with hydrogen peroxide in the presence of solid zeolite catalyst (titan-silicate-zeolite) was chosen by Radoiu et al. [57] as a model heterogeneous liquid-phase reaction for study of microwave effects, Scheme 10.12. 

A number of zeolite syntheses result in incomplete conversion of all of the gel components to solid zeolite. In many cases the reactant Si/Al ratio is different than that of the product (usually higher), resulting in a silicate solution remaining behind. At the industrial scale this silicate solution is often recycled to minimize waste and raw material cost [34—36]. 

Microporous solids, zeolites in particular, are widely used in heterogeneous catalytic processes, separations, oil recovery, and other industrial processes (i). A microscopic... 

Defects in Solids Dielectric Polarizabilities of Oxides Fluorides Diffraction Methods in Inorganic Chemistry Electronic Stmcture of Solids Fluorides Solid-state Chemistry Halides Solid-state Chemistry Intercalation Chemistry Non-crystalUne Solids Oxides Solid-state Chemistry Phosphates Solid-state Chemistry Polyphosphazenes Sol-Gel Synthesis of Solids Solids Computer Modeling Stmcture Property Maps for Inorganic Solids Zeolites. 

Self-assembled Inorganic Architectures Sol-Gel Synthesis of Solids Zeolites. 

Thus, the catalytic cracking of PET has been recently a subject of interest [26], Several acid solids (zeolites 4A and 13X and alumina) as well as metal salts (CuCh, MgCE and Zn, Sn, Mg, Mn acetates) have been tested as catalysts at 400-500°C. Copper chloride has been found as the most effective catalyst, reducing the degradation time by almost 3.5 times in regard to the thermal treatment and minimizing the amount of carbonaceous residues. 

Among the above-mentioned solids, zeolites have been certainly the most studied catalysts for polyolefin cracking. Zeolites are crystalline microporous aluminosilicates of groups lA or IIA elements (mainly sodinm, potassinm, magnesium, calcium) whose chemical composition may be represented by the following formnla [60] ... 

The second aspect which makes the interest of the study of zeolites by XPS is that it allows to understand many unexpected aspects of this spectroscopy, in particular when applied to solids. Zeolites in many respects are materials which may be regarded as model solids and not only because of their regular pore structure. Indeed by varying the Si/Al ratio, the nature of counter cations, the ion exchange level, the occlusion of extraframework phases, such properties as the density and strength of acidic or basic sites may be varied in a predictable fashion. All these variations are reflected in the XPS spectra yielding data... 

Microporous solids Zeolites are solids with aluminosilicate frameworks having pores and channels. When these are occupied by hydrated ions the compounds are used as ion exchangers when the pores are empty they have useful catalytic properties. 

Benzylnaphthalenes are used as synthetic intermediate for the production of dyes [1]. Traditionally, these reactions are carried out using Lewis acid catalysts (AICI3, ZnCh) which are less selective compared to the solid zeolite catalysts. In addition, homogeneous catalysts have several disadvantages difficulty in catalyst recovery and use of stoichiometric amount of the catalyst with respect to the benzylating agent. 

The following approaches will be addressed (1) H202-assisted decomplexation of metallo-organic salts for ion-exchange, (2) om-pot synthesis of metal-exchanged-zeolites, and finally (3) room-temperature detemplation of parous solids (zeolites and mesoporous materials). The Fe-catalysts are comptued on the basis of their NaO-decomposition performance, both in pure N20/He and under simulated industrial conditions for nitric acid plants containing O2, NO and H2O. 

Hydroxylation of phenol by hydrogen peroxide over solid acids exhibits an autocatalysis that has never been described in earlier works. The induction period is dependent on the acidity and is reduced by initial addition of dihydroxybenzenes or other electron-transfer agents. A new mechanism, initiated by the slow formation of dihydroxybenzenes in the induction period, should be considered. Comparison of various catalysts shows that the reaction is also dependent on the structure of the solid. Zeolites with too small a porosity are not active, according to a large space demand of the reaction. Catalysis by titanium silicalites does not show such behaviour the reactivity is low but regular. Thus, our results show that valuable comparison between catalysts cannot be deduced from tests performed by stopping the reaction at a determined time, but that kinetic studies are essential. 

A naive description of the main steps of a reactive event can be sketched two reactants approach each other in the reaction medium, and the result of such approach (collision) may or may not lead to the products, depending both on the molecular states and reciprocal orientation and the interactions with the medium. While liquid phase reactions are favourite in laboratories, solid matrices are also used as reaction media. Among solids, zeolites, with their arrays of molecular sized cages and channels, are used as reaction pots in many synthetic processes both in research laboratories and in large scale industrial plants. 

Zeolites occur widely in nature and have been known for more than 250 years as aluminosilicate minerals, i.e., faujasite, mordenite, offretite, ferri-erite, chemierionite, and chabazite. Zeolites are inorganic crystalline solids with small pores (1-20 A diameter) running throughout the solid. Zeolites... 

Zeolite Catalysts. Only a few examples are known for liquid-phase carbonylation in the presence of solid zeolite catalysts. It was fovmd that catalytic carbonylation of a large amount of tert-butyl alcohol relative to the acidic sites of the H-zeolites in organic solvents (chlorobenzene, re-hexane, benzene) requires an elevated temperature and CO pressure (62). 

Sorption affinity of fluid components with molecular sieves is governed by the type of their mutual interactions, i.e., fluid-solid interactions, on the microphysical level. For the sorption systems given, besides van der Waals-type atom-atom dispersion interactions of all types of molecules involved, with the solid, zeolitic ion-dipole interactions for H2O, H2S and COS as well as zeolitic ion-quadrupole interaction for CO2 have to be taken into account. A measure of the overall strength of interaction energy is the isosteric heat of sorption, qisosteric-This quantity differs from the differential heat of sorption or sorption enthalpy, - AH, usually measured calorimetrically, by the mechanical work term, RT qisosteric AH -t RT. 

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